Concrete exhibits time-dependent strains due to creep and shrinkage.
Creep and shrinkage have a considerable impact upon the
performance of concrete structures, causing increased deflections
as well as affecting stress distribution. Creep in concrete represents
dimensional change in the material under the influence of
sustained loading. In addition, whether subjected to load or not,
concrete contracts on drying undergoes shrinkage. In the case of
many actual structures, creep and shrinkage occur simultaneously
and the treatment of the two together is often convenient from a
practical point of view. Failure to include creep and shrinkage
effects in the analysis of the structures may lead to excessive
deformation and wide spread cracking.
In general, time-dependent deformations of concrete may severely
affect the serviceability, durability, and stability of the
structure. Calculation of creep and shrinkage deformations is difficult.
Various researchers have carried out extensive work to
quantify and predict the effects of creep and shrinkage. The experimental
studies have been conducted in specific environments
and for different durations varying from 7 to 5,000 days. Therefore,
the results are not in close agreement with each other,
though they satisfied the specific conditions in which the tests
were carried out. Nevertheless, due to this extensive research
work, significant advances have been achieved in the knowledge
about creep and shrinkage of concrete.